The present application relates to heavy vehicle braking, and is particularly directed to a driver braking demand indicator apparatus for a heavy vehicle, such as a truck.
A known method of indicating driver braking demand is determining the extent of travel of a plunger of a foot brake valve of the truck. When the driver desires to operate the vehicle service brakes, the driver applies a foot to a brake pedal which, in turn, causes travel movement of the plunger. A drawback in using the plunger travel method is that sensitivity of the foot brake valve (i.e., delivery pressure/travel distance) increases significantly at higher levels of driver braking demand. This high sensitivity makes it difficult to determine the driver's intended braking demand using only travel movement of the plunger. Another drawback in using the plunger travel method is that additional mechanical components are required. These mechanical components would otherwise not be needed in a typical foot brake valve.
Another known method of indicating driver braking demand is determining valve delivery pressure in a braking circuit of the foot brake valve of the truck. A drawback in using the valve delivery pressure method is the absence or lack of information about the driver's intent to slow the truck during initial stages of pedal movement. This occurs because there needs to be at least some movement of the brake pedal and at least some travel movement of the plunger before valve pressure is actually delivered. It would be desirable to provide an apparatus and method of indicating driver braking demand which overcomes drawbacks of known methods of indicating driver braking demand.